In rotary regenerative heat exchange apparatus, a mass of heat absorbent element commonly comprised of packed element plates is first positioned in a hot gas passageway to absorb heat from hot gases passing therethrough. After the plates become heated by the hot gases they are moved into a passageway for a cool fluid such as air where the hot plates give up their heat to cool air or other gas passing therethrough.
The heat absorbent material is carried in a rotor that rotates between the hot and cool fluids, while fixed housing structure including sector plates at opposite ends of the rotor is adapted to surround the rotor and direct the hot and cool fluids therethrough. To prevent mingling of the hot and cool fluids, the end edges of the rotor are provided with flexible sealing members that rub against adjacent surface members of the rotor housing to resiliently accommodate a limited degree of rotor "turndown" or other distortion caused by mechanical loading and thermal distortion of the rotor.
To permit turning the rotor freely about its axis, certain minimum clearance space between the rotor and adjacent housing structure is required, however, excessive clearance space is to be avoided because it will result in excessive leakage through the space therebetween. However, uneven expansion between the rotor and rotor housing may open a path for excessive leakage and a lower effectiveness may result.
The expansion of the rotor and adjacent housing structure assumes greatest proportions directly adjacent the inlet for the hot fluid where the rotor and rotor housing are both subjected to a maximum amount of thermal expansion and distortion. An arrangement that compensates for a loss of sealing effectiveness at this, the "hot" end of the rotor, is shown by U.S. Pat. No. 3,786,868 where a plane sector plate is pivoted about a fulcrum carried by the housing. Other patents represented by U.S. Pat. No. 3,404,727 separate a sector plate into radially adjacent sections, and then counter-balance each section into a preferred relationship with the adjacent face of the rotor.
Although the arrangements defined are partially effective in reducing some leakage of fluid through the clearance space between the rotor and adjacent sector plate, leakage continues to be a major problem because each portion of the sector plate expands linearly while the face of the rotor lying adjacent thereto expands both radially and axially to assume a dished configuration. Therefore, an increase of temperature usually indicates a differential of expansion and an increase in the amount of fluid leakage between the several relatively rotatable parts of the rotor.